1. Field of the Invention
The present invention relates generally to surfaces which interface with a fluid such as a gas or liquid under conditions where there is relative motion between the fluid and the surface. More particularly the invention relates to the application of dimples or cavities to such surfaces. Still more particularly, the invention relates both to vehicles which are intended to move within a fluid and to the application of dimples to their external surfaces which interface with the fluid through which the vehicle moves, and to conduits within which fluids flows and to the application of dimples to their internal surfaces which interface with the flowing fluid.
For the purposes of this specification the term vehicle is intended to include internally or externally powered objects as diverse as automobiles, boats including the displacement, planing and hydrofoil types and airplanes, fans and propellers, bullets and artillery shells all of which have surfaces which move relative to one or more fluids; and to objects which move within a relatively dense gas at one time and in a vacuum or highly rarified gas at other times.
Within this specification the terms air and gas will be employed interchangeably to refer to a single gas or a mixture of gasses including but not restricted to air and all its constituent gasses and to any other gas or gas-like material which moves relative to a surface. The term fluid will be employed to refer to any liquid or any gas.
The term lost energy is not intended to imply that energy is lost but simply that energy of motion is converted to another form of energy such as heat.
2. Background of the Invention
Whenever energy is used either to propel a vehicle through a fluid or to propel a fluid through a conduit, there is energy lost because of friction between the surface and the fluid moving relative to it. The lost energy is generally evidenced by conversion of the energy lost to heat and by a slowing of the vehicle or by a pressure drop of the fluid flowing through the conduit. The lost energy must be constantly replaced to maintain the speed of the vehicle or to maintain the pressure of the fluid. In a vehicle, replacing the lost energy is achieved by supplying power to the wheels or other propelling agency such as a propeller or jet engine. In a conduit the lost energy is replaced either by increasing the initial pressure of the fluid being pumped through a conduit or by providing pumping means spaced at intervals along a pipe or conduit to increase to a higher level the pressure which had dropped to a lower level through friction.
To the extent that friction between a surface and a fluid flowing relative to the surface can be reduced, the energy required to move the vehicle through the fluid or the fluid through the conduit can be reduced. Such an energy reduction will be represented by an increase in gas mileage and range in an internally powered vehicle such as a car or boat or plane or rocket or by an increase in range of an externally powered vehicle such as an artillery shell or bullet.
Further, lift is generated by fluid flow over dimpled surfaces as compared with fluid flow over similarly contoured smooth or undimpled surfaces. The lift is generated because fluid, traversing the dimpled surface, must travel further over the dimples than over a corresponding contoured smooth surface, thereby generating higher fluid velocity and lower pressure adjacent the dimpled surface, in accord with Bernoulli's theorem, whereby lift is generated by the differential pressure between the lower pressure adjacent the surface having the dimples and the higher pressure on the corresponding undimpled or smooth surface positioned on the vehicle oppositely to the dimpled surface.
3. Related Art
The only related art known to me is a golf ball which has a dimpled surface. A typical golf ball is 1.67 inches in diameter (42.5 mm) and has distributed, more or less uniformly, over its surface 326 dimples or shallow cavities each about 0.138 inches in diameter (3.5 mm) and about 0.03 inches (0.8 mm) deep. The surface area of the golf ball is approximately 8.76 square inches (5652 mm.sup.2). Therefore the density of the cavities is about 37 per square inch (0.057/mm.sup.2).
No other application of cavities or dimples of any size or shape to the exterior surface of a vehicle of any sort moving in a gas or liquid or to the interior surface of a conduit through which a fluid flows is known to me.